| The structure and function of a variety of cells including plant, animal and microbial cells are studied to appreciate that cells are functional living units. While specialised cells are used to exemplify variety, the detailed structure and function of these are dealt with in the context of other units, e.g. in Animal Physiology. |
1. Cell structure and function
| a. Similarities and differences between animal, plant and microbial cells. | Cheek epithelial cells, leaf mesophyll cells and yeast cells should be used to illustrate typical plant, animal and microbial cells, their similarities and differences in structure. | |
| b. Function of cell structures. | Functions of:
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Examine fresh and prepared slides of a range of plant, animal and microbial cells using appropriate stains and a light microscope. Suitable examples would include: cheek epithelium, onion epidermis, rhubarb epidermis, Elodea, yeast. |
| c. Commercial and industrial uses of cells. | ||
| i. Bread making. | Anaerobic respiration in yeast produces carbon dioxide gas which causes dough to rise. | Select and present data on the commercial and industrial uses of micro-organisms. |
| ii. Alcohol production | Fermentation in yeast results in the production of alcohol (beer and wine). | |
| iii. Antibiotic production. | Fungi used to produce wide range of antibiotics that can destroy bacteria. Resistant bacteria are unaffected by antibiotics and are on the increase due to overuse of antibiotics. |
Carry out experiments to demonstrate the effects of antibiotics on bacterial colonies. |
| iv. Yoghurt production. | Bacteria convert sugar in milk (lactose) into lactic acid, causing curdling. | Carry out an experiment to demonstrate lactic acid production by yoghurt bacteria. |
| v. Alternative fuel production. | Biogas is produced when bacteria respire anaerobically to produce methane from waste products Gasohol is produced when alcohol produced by the fermentation of sugar cane is mixed with petrol. |
2. Diffusion and osmosis in plant and animal cells
| a. Diffusion as the movement of substances from a high concentration to a low concentration down a concentration gradient. | Examples of substances which enter and leave the cell by diffusion, e.g.
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Carry out an experiment to demonstrate diffusion. |
| b. The importance of diffusion to cells. | To gain raw materials for respiration and photosynthesis. To remove waste products. |
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| c. Osmosis as a ‘special case’ of diffusion of water. | Osmosis defined as the movement of water across a selectively permeable membrane as a result of a water concentration gradient. | |
| d. Osmotic effects in plant and animal cells. | Osmotic effects in plant and animal cells explained in terms of the movement of water down a water concentration gradient The effects of placing plant and animal cells in hypertonic, hypotonic and isotonic solutions should be studied. The terms plasmolysed, turgid and flaccid should be known. |
Carry out experiments to demonstrate osmosis using Visking tubing, model cells and potato or other plant material. Microscopic examination of rhubarb epidermis or red onion cells in different concentrations of solutions. |
| 1. Enzyme properties | ||
| a. Properties of catalysts and enzymes | The properties and functions of catalysts:
Enzymes are biological catalysts made by all living cells. |
Demonstrate the breakdown of hydrogen peroxide by heating compared to catalysis with manganese dioxide and catalase. |
| b. Specificity of enzymes for their substrates. | The characteristic shape of enzyme molecules complementary to their substrate. Presence of specific active site | Carry out an experiment to demonstrate the specificity of enzymes. |
| c. Enzymes involved in degradation and in synthesis. | Degradation: the chemical breakdown of a substance as illustrated by amylase and catalase. Synthesis: the building of a complex molecule from simpler molecules as illustrated by phosphorylase. Details of their substrates and products are required. |
Carry out an experiment to demonstrate the synthesis of starch. |
| d. Factors affecting activity | The influence of temperature and pH on enzyme activity giving rise to optimum operating conditions and denaturing (protein structure alters resulting in change in shape of active site and in activation of enzyme). | Plan and design investigations into the influence temperature and pH on enzyme activity. |
4. Aerobic and anaerobic respiration
| a. Energy release | ||
| i. Glucose as a source of energy in the cell. | The chemical energy stored in glucose is released by a series of enzyme-controlled reactions called respiration. Some energy is released as heat from cells during respiration but most is used for cellular activities such as:
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Select and present data on the energy content of foods. |
| ii. Role of ATP | Energy released from the breakdown of glucose is used to synthesise ATP from ADP and Pi (inorganic phosphate). The ATP can then be used by the cell as an energy source. |
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| b. Comparison of energy yield in aerobic and anaerobic respiration. | Aerobic respiration yields 38 molecules of ATP per glucose molecule. Anaerobic respiration yields 2 molecules of ATP per glucose molecule. |
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| c. Products | ||
| i. Aerobic Pathway. | Breakdown of glucose to pyruvic acid by glycolysis. Further breakdown of pyruvic acid to carbon dioxide and water in presence of oxygen. |
Plan and design an investigation into anaerobic respiration in yeast. |
| ii. Anaerobic Pathway. | Breakdown of glucose to pyruvic acid by glycolysis. Reversible anaerobic conversion of pyruvic acid to lactic acid in animals. Effect of lactic acid on muscle cells (i.e. muscle fatigue) and subsequent repayment of oxygen debt. Irreversible anaerobic conversion of pyruvic acid to ethanol and carbon dioxide in plants and yeast. |
| a. Energy fixation | Photosynthesis is a series of enzyme-controlled reactions which allow green plants to make their own food. | |
| i. Sunlight as the source of energy. | The light energy from the sun is trapped by chlorophyll in the chloroplasts and is converted into chemical energy in the form of ATP which is used in the production of glucose. | |
| ii. Summary equation for photosynthesis. | Carbon dioxide and water as raw materials for the production of glucose and oxygen as a by-product. Occurs in the presence of chlorophyll and light. The importance of diffusion in the movement of carbon dioxide and oxygen into and out of the leaf cells. |
Carry out experiments to compare photosynthesis in light and dark conditions and in the presence and absence of carbon dioxide. |
| iii. Photosynthesis as a set of two summary reactions: photolysis followed by carbon fixation. | Photolysis as the breakdown of water to provide hydrogen, ATP and oxygen. The oxygen is released as a by-product and the hydrogen is picked up by a hydrogen carrier molecule (specific name not required). Carbon fixation as the combining of the hydrogen produced by photolysis with carbon dioxide to form glucose using the ATP produced during photolysis. |
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| iv. Conversion of glucose to other carbohydrates. | Starch as a storage carbohydrate and cellulose as a structural component of the cell wall. | |
| b. Factors affecting rate of photosynthesis | ||
| i. Limiting factors. | Limiting factors are:
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Carry out experiments using Elodea to demonstrate the effect of limiting factors.Use computer simulations which illustrate the effect of limiting factors. |
| ii. Production of early crops in horticulture. | The use of supplementary lighting, carbon dioxide enrichment and heating to produce early crops in horticulture. |
Unit 2: Environmental Biology and Genetics
| Environmental biology and genetics are of considerable economic and social importance. This unit focuses on the importance of biodiversity and illustrates this through a study of ecology which explores energy flow and the factors that affect the variety of species in an ecosystem. The contribution to biodiversity by variation within a species is illustrated through the study of fertilisation and genetics. |
| a. Energy flow | ||
| i. Components of an ecosystem. | Habitats, populations and communities as components of an ecosystem. The niche of an organism within an ecosystem. |
Use a case study of a local or topical ecosystem to identify its component parts and interrelationships. |
| ii. Food chains and food webs. | Producers, primary and secondary consumers, herbivores, carnivores, omnivores, predators, prey and decomposers in ecosystems as illustrated in food chains and food webs. The flow and loss of energy in ecosystems as seen in food chains. Pyramids of energy, numbers and biomass in ecosystems. |
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| b. Factors affecting the variety of species in an ecosystem | ||
| i. The importance of biodiversity at species level. | Biodiversity defined as the range of species in an ecosystem. A species defined as a group of organisms which can interbreed to produce fertile offspring. A stable ecosystem has a wide range of species and food webs. The removal of one or more species and the consequences this has on other organisms/populations in the food web. |
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| ii. Factors affecting biodiversity. | ||
| Adaptations to habitat and niche. | As illustrated by
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| Effects of grazing | High intensity of grazing will maintain species diversity. Very high or low intensity of grazing will decrease diversity. | |
| Effects of human activity. | Pollution and habitat destruction lead to decrease in species diversity. | |
| Competition in plants and animals. | Plants compete mainly for water, light and soil nutrients. Animals compete for food (e.g. predator prey interactions), water and shelter. |
Design and carry out experiments to demonstrate the effects of competition on population growth using for example, cress or radish seedlings. |
| iii. Behavioural adaptations in animals and their adaptive significance. | As illustrated by responses to light and relative humidity in woodlice. | Carry out experiments to demonstrate animal responses to environmental stimuli, using choice chambers or similar apparatus. |
2. Factors affecting variation in a species
| a. Variation | Continuous and discontinuous variation using examples in both plants and animals. | |
| b. Fertilisation. | ||
| Gamete (sex cell) production | ||
| Site of production of male and female gametes in mammals. | Mammals:
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| Site of production of male and female gametes in flowering plants. | Flowering plants:
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| i. Fusion of nuclei. | Fusion of nuclei forms a zygote producing variation by random combination of parental gamete | |
| c. Genetics | ||
| i. The importance of chromosome structure to an organism’s characteristics. | Chromosomes contain genetic information that gives rise to an organism’s characteristics. Chromosomes should be described in terms of a chain of DNA bases. |
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| The relationship between DNA sequence and protein synthesised. | The order of DNA bases encodes information for the sequences of amino acids in proteins. These in turn dictate the structures and therefore functions of these proteins. |
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| The relationship between proteins present in a cell and the organism’s characteristics. | e.g. the protein haemoglobin gives red blood cells their characteristic colour. Role of enzymes and hormones. |
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| ii. Division of the nucleus in gamete production (meiosis). | Gametes have one set of chromosomes. Body cells have two matching sets of chromosomes. The reduction in number of chromosomes to a single set occurs during gamete formation. The two sets of chromosomes are restored at fertilisation. Matching chromosomes pair and then separate during meiosis. The random assortment of chromosomes during meiosis leads to variation in offspring. |
Use a card simulation to show random assortment of chromosomes. |
| iii. Chromosome numbers in different species. | Humans have 23 chromosomes in one set giving a total of 46 chromosomes in a normal body cell. Different species have different numbers of chromosomes (chromosome complement). |
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| iv. Sex determination. | In humans, each male gamete has an X or a Y chromosome, while each female gamete has an X chromosome. | |
| v. Characteristics controlled by forms of a gene called alleles. | Genes are parts of chromosomes. Different forms of a gene are called alleles. Each gamete carries one allele of the gene. Use of the terms homozygous, heterozygous, dominant and recessive. |
Select and present information to show that characteristics are inherited from both parents. |
| vi. Genotype and phenotype | Relationship of genotype to phenotype. Examples of the same phenotype with different genotypes. |
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| vii. Monohybrid crosses. | Use of terms true breeding, P, F1 and F2 | Solve problems related to monohybrid crosses in plants and animals. |
| Parents in experimental monohybrid crosses are usually true breeding and show different phenotypes. | ||
| Solve problems in relation to monohybrid crosses following through from the P generation to the F2 generation, using dominant and recessive alleles | Use computer models to illustrate monohybrid crosses. | |
| viii. Proportions and ratios of phenotypes of the F1 and F2 offspring. | Reasons for differences between observed and predicted figures in monohybrid crosses should be known. | Germinate albino and wild type tobacco seeds and their offspring to illustrate the proportions of phenotypes of the F1 and F2 offspring. |
| ix. Co-dominance. | Two alleles of a gene can be co-dominant when neither is dominant nor recessive. Both alleles are displayed in the phenotype. Candidates should be able to solve problems related to crosses involving co-dominant alleles. |
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| x. Polygenic inheritance. | A range of phenotypes is produced e.g. skin colour in humans, and seed mass in plants. The characteristics arise due to the interaction of the alleles of several genes. |
Solve problems in relation to genetic crosses involving co-dominant alleles. |
| xi. Environmental impact on phenotype. | The final appearance of an organism (phenotype) is the result of its genotype and the effects of the environment. If organisms of identical genotype are subject to different environmental conditions they show considerable variation. Such changes have little evolutionary significance as they are not passed from one generation to the next. |
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| xii. Natural selection. | The process by which organisms that are better adapted to their environment survive and breed, while those less well adapted fail to do so. The better adapted organisms are more likely to pass their characteristics to succeeding generations as illustrated by the Peppered Moth. |
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| xiii. Selective Breeding. | The selective breeding of plants and animals showing desirable characteristics.
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| xiv. Genetic Engineering. | ||
| Stages in the production of desired product by genetic engineering. | To include the following stages:
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Select, present and discuss information on the applications and issues arising from genetic engineering. |
| Applications of the products of genetic engineering. | Production of medicines for human use e.g. insulin and growth hormone. | |
| Advantages and disadvantages of genetic engineering. | Advantages to include increased range of products and increased rate of production. Disadvantages to include the possible release of genetically engineered bacteria into the environment and cost of development. |
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| This unit explores the ways in which animals are adapted for survival and respond to changes in their internal and external environments. The emphasis is on vertebrates, particularly mammals, and explores the relationship between structure and function. |
| a. Breakdown of food | ||
| i. Requirement for food. | The main food groups:
Simple structure of carbohydrates, proteins and fats in terms of chemical elements present, simple sugars, amino acids, fatty acids and glycerol. |
Select and present information on the incidence of carbohydrates, proteins and fats in common foodstuffs. |
| ii. Food tests for starch, glucose, protein and fat. | ||
| iii. Energy content of food. | Different food groups have different energy contents e.g. fat contains more energy than protein and carbohydrate. | |
| iv. The need for digestion. | Digestion involves:
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Carry out an experiment to demonstrate the purpose of digestion and absorption using Visking tubing as a model gut. |
| b. The structure and function of the alimentary canal and associated organs. | ||
| i. The mouth, salivary glands and oesophagus. | The mechanical breakdown of food in the mouth. · Saliva contains amylase which digests starch into maltose. · Mucus in saliva from salivary glands helps lubricate mouth and food to aid swallowing. · Oesophagus and the mechanism of peristalsis. It should be noted that peristalsis occurs throughout the length of the alimentary canal and not just in the oesophagus. Details of the teeth are not required. | Select and present information to illustrate peristalsis. |
| ii. The role of the stomach. | Food is churned in the stomach by the action of longitudinal and circular muscles to mix food with gastric juices. Chemical breakdown of protein by pepsin. Functions of mucus-secreting cells, enzyme secreting cells, and acid-secreting cells. | Design and carry out experiments to demonstrate the effects of pH and temperature on the digestion of protein. |
| iii. The role of the small intestine in the absorption and secretion of food. | To include further digestion of fat by lipase and protein by trypsin. The absorption of food by diffusion.The structure of a villus, including · the lacteal · blood capillaries · the food molecules each absorbs. The fate of absorbed materials to include · storage, · energy source, · raw materials for synthesis · deamination. | Examine slides of villi. |
| iv. The role of the pancreas, liver and gall bladder. | Pancreas produces lipase, trypsin and amylase for fat digestion. Liver stores excess glucose as glycogen and is the site of deamination. Gall bladder stores bile which emulsifies fats to aid digestion. | |
| v. The role of the large intestine, rectum and anus. | Water absorption and elimination of undigested material. | Select and present information to illustrate the incidence of colonic cancer in Scotland. |
2. Control of the internal environment
| i. The structure of the human urinary system. | To include · kidney, · renal artery, · renal vein, · ureter, · bladder · urethra. | Select and present data relating water consumption to volume and concentration of urine. |
| ii. The role of the mammalian kidney. | ||
| Osmoregulation. | Osmoregulation is the regulation of water content in organisms. The kidneys as main organs for osmoregulation in mammals. Water gain through · drinking, · food · metabolic water; water loss through · sweat, · breath, · faeces and · urine. | |
| Production of urea and its removal in urine. | The role of the urine in the excretion of nitrogenous waste. Urea as the waste product from breakdown of excess amino acids in the liver i.e. · deamination, · its transportation in the blood to the kidney · removal in urine. | |
| The structure and function of the kidney. | To include filtration, reabsorption and urine production in the kidney as related to the structure of the nephron, including · the Bowman’s capsule, · glomerulus, · blood capillaries · collecting duct. | |
| iii. Negative feedback control by ADH. | Osmoreceptors in the hypothalamus are stimulated by a change in water concentration in the blood. A decrease in water concentration triggers an increase in the release of antidiuretic hormone (ADH) from the pituitary.· ADH increases the permeability of the kidney tubules and collecting duct, · resulting in more water being reabsorbed into the blood stream. · As the water concentration of the blood rises:o less ADH is released resulting in less water being reabsorbed. o Concentration and volume of urine produced as a result. | Select and present information on the role of ADH. |
| iv. Osmoregulation in marine and freshwater bony fish. | Marine bony fish: hypotonic tissues, · dehydration problem, · overcome by drinking water and excreting excess salt and small volume of concentrated urine. Freshwater bony fish: hypertonic tissues, · problem of influx of water, · overcome by excreting copious and very dilute urine. | |
3. Circulation and gas exchange
| a. The structure and function of the heart and blood vessels | ||
| i. The structure of the heart related to its function as a muscular pump. | The structure of the heart including: · the names of the four chambers of the heart; · the position and function of valves (bicuspid, tricuspid and semilunar); · the reason for the differences in thickness of walls of the ventricles; · the heart obtains its blood supply from the coronary arteries. · The effect of blocked coronary artery. | View and discuss video material on circulation. Examine a mammalian heart to identify structures and relate to their function. |
| ii. Blood vessels. | The path of blood flow through the heart and its associated vessels; · blood leaves heart in arteries, · flows through capillaries · and returns to heart in veins; · the pulse indicates that blood is pumped through arteries; structural adaptations of arteries, veins and capillaries related to function. Names and positions of pulmonary artery and vein, aorta and vena cava, hepatic artery, hepatic vein, mesenteric artery, hepatic portal vein, renal arteries and renal veins. | |
| b. Structure and function of lungs in gas exchange and the capillary network | ||
| i. Internal structure of lungs and features which make them efficient gas exchange structures. | Structure to include trachea, bronchi, bronchioles and alveoli (air sacs).Features of alveoli which allow efficient gas exchange: · large surface area · thin walls · moist surfaces · good blood supply. The role of diffusion in exchange of oxygen and carbon dioxide. | |
| ii. Features of capillary network which allow efficient gas exchange in tissues | To include large surface area, in close contact with tissue cells, thin walled. | View and discuss video material on gas exchange. |
| c. Composition and functions of blood | ||
| i. Function of red blood cells and plasma in the transport of respiratory gases and food. | Oxygen carried in red blood cells, carbon dioxide carried in red blood cells and dissolved in plasma. Concentration of carbon dioxide carried dissolved in plasma is limited by the increase in acidity carbon dioxide causes in the blood. Soluble foods carried dissolved in the plasma. | Examine prepared blood smears. |
| ii. Function of haemoglobin in the transport of oxygen. | Ability of haemoglobin to combine with oxygen to form oxyhaemoglobin at high oxygen levels in the lungs and to release oxygen at low oxygen levels in the tissues. | |
| iii. Functions of macrophages and lymphocytes in defence. | Phagocytosis by macrophages. Stages of phagocytosis (engulfing, then digestion). No requirement to name pseudopodia and lysosomes. Antibody production and specificity of antibodies | |
4. Sensory mechanisms and processing of information
| a. The structure and function of the brain | ||
| i. Functions, in simple terms, of cerebrum, cerebellum, medulla and hypothalamus. | Structures to include cerebrum, cerebellum, medulla and hypothalamus. · Cerebrum as the site of conscious responses and higher centres · cerebellum as the centre of balance and co-ordination of movement · medulla as the site of the vital centres such as breathing and heart rate · hypothalamus as the centre for regulation of water balance and temperature. | |
| ii. Discrete areas of cerebrum related to sensory/motor function. | Location of sensory and motor strip as discrete areas of the cerebrum. | |
| b. The structure and function of the nervous system | ||
| i. The brain, spinal cord and nerves. | Nerves carry impulses from the senses to the central nervous system and impulses from the central nervous system to the muscles. | Demonstrate and explain a reflex action. |
| ii. Reflex action and the reflex arc. | Reflex arc as: · Receptor · sensory neurones· relay fibre · motor neurone · effector. Detailed structure need not be known. Rapidity and protection as function of reflex response. | Demonstrate and explain a reflex action. |
| iii. The role of the central nervous system (CNS) | To include: sorting out information (in the form of impulses) from the senses and sending messages (in the form of impulses) to muscles which can make the appropriate response. | Carry out an investigation into changes in body surface temperature in changing environmental conditions. |
| iv. Temperature regulation as a negative feedback mechanism. | To include changes of temperature · motor responses · constriction and dilation of blood vessels · alterations in blood flow to the skin · shivering, sweating and consequent changes in body temperature. |
